RT Journal Article SR Electronic T1 A SENSITIVE ENZYMATIC ASSAY FOR DOPAMINE-β-HYDROXYLASE JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 425 OP 431 VO 178 IS 3 A1 PERRY B. MOLINOFF A1 RICHARD WEINSHILBOUM A1 JULIUS AXELROD YR 1971 UL http://jpet.aspetjournals.org/content/178/3/425.abstract AB A sensitive and convenient procedure for the determination of dopamine-β-hydroxylase (DBH) activity in homogenates of sympathetically innervated organs is described. The assay uses either phenylethylamine or tyramine as substrate and is based on the sequential conversion of the product of the DBH reaction to a radioactively labeled N-methyl derivative by reaction with partially purified bovine adrenal phenylethanolamine-N-methyltransferase in the presence of S-adenosyl-l-methionine methyl-14C. The N-methyl derivatives are separated by solvent extraction and their radioactivity is determined. The identity of the reaction products has been determined chromatographically, and the characteristics of the two enzymatic steps in the assay procedure are defined. Endogenous tissue inhibitors of DBH must be inactivated by cupric ions prior to determination of the enzyme activity. DBE activity in sympathetically innervated tissues of the rat has been measured. © 1971 by The Williams & Wilkins Co.